WAAARRRNIIIIIIING

If you set up a Japanese account to download Petit Switch, be absolutely sure that you continue to use the Japanese account when coding your game.

DON'T do what I did, and go "Well, it works in my Jayenkai account.. I'll carry on with that"

Because, when you go to upload your finished game, you hit a great big wall..
The account you bought it with gets (I think) 10 "Upload" slots.
You can "purchase Slots" for other users.. .. Except my default account can't do that, because it can't access the Japanese eShop, so can't upload ANYTHING!!!

*screenshots the entire code, and prepares to 1980's style "Type-in" type it all back in again, using the other account.

...
FFS..